# Package Collection

Package collections are short, curated lists of packages and associated metadata that can be imported
by SwiftPM to make package discovery easier. Educators and community influencers can publish
package collections to go along with course materials or blog posts, removing the friction of using
packages for the first time and the cognitive overload of deciding which packages are useful for
a particular task. Enterprises may use collections to narrow the decision space for their internal
engineering teams, focusing them on a trusted set of vetted packages.

## Creating a Package Collection

A package collection is a JSON document that contains a list of packages and metadata per package.

To begin, define the top-level metadata about the collection:

* `name`: The name of the package collection, for display purposes only.
* `overview`: A description of the package collection. **Optional.**
* `keywords`: An array of keywords that the collection is associated with. **Optional.**
* `formatVersion`: The version of the format to which the collection conforms. Currently, `1.0` is the only allowed value.
* `revision`: The revision number of this package collection. **Optional.**
* `generatedAt`: The ISO 8601-formatted datetime string when the package collection was generated.
* `generatedBy`: The author of this package collection. **Optional.**
    * `name`: The author name.
* `packages`: A non-empty array of package objects.

#### Add packages to the collection

Each item in the `packages` array is a package object with the following properties:

* `url`: The URL of the package. Currently only Git repository URLs are supported. URL should be HTTPS and may contain `.git` suffix.
* `summary`: A description of the package. **Optional.**
* `keywords`: An array of keywords that the package is associated with. **Optional.**
* `readmeURL`: The URL of the package's README. **Optional.**
* `license`: The package's *current* license information. **Optional.**
    * `url`: The URL of the license file.
    * `name`: License name. [SPDX identifier](https://spdx.org/licenses/) (e.g., `Apache-2.0`, `MIT`, etc.) preferred. Omit if unknown. **Optional.**
* `versions`: An array of version objects representing the most recent and/or relevant releases of the package.

#### Add versions to a package

A version object has metadata extracted from `Package.swift` and optionally additional metadata from other sources:

* `version`: The semantic version string.
* `summary`: A description of the package version. **Optional.**
* `manifests`: A non-empty map of manifests by Swift tools version. The keys are (semantic) tools version (more on this below), while the values are:
    * `toolsVersion`: The Swift tools version specified in the manifest.
    * `packageName`: The name of the package.
    * `targets`: An array of the package version's targets.
        * `name`: The target name.
        * `moduleName`: The module name if this target can be imported as a module. **Optional.**
    * `products`: An array of the package version's products.
        * `name`: The product name.
        * `type`: The product type. This must have the same JSON representation as SwiftPM's `PackageModel.ProductType`.
        * `target`: An array of the product’s targets.
    * `minimumPlatformVersions`: An array of the package version’s supported platforms specified in `Package.swift`. **Optional.** 

```json
{
  "5.2": {
    "toolsVersion": "5.2",
    "packageName": "MyPackage",
    "targets": [
      {
        "name": "MyTarget",
        "moduleName": "MyTarget"
      }
    ],
    "products": [
      {
        "name": "MyProduct",
        "type": {
          "library": ["automatic"]
        },
        "targets": ["MyTarget"]
      }
    ],
    "minimumPlatformVersions": [
      {
        "name": "macOS",
        "version": "10.15"
      }
    ]
  }
}
```

* `defaultToolsVersion`: The Swift tools version of the default manifest. The `manifests` map must contain this in its keys. 
* `verifiedCompatibility`: An array of compatible platforms and Swift versions that has been tested and verified for. Valid platform names include `macOS`, `iOS`, `tvOS`, `watchOS`, `Linux`, `Android`, and `Windows`. Swift version should be semantic version string and as specific as possible. **Optional.**

```json
{
  "platform": {
    "name": "macOS"
  },
  "swiftVersion": "5.3.2"
}
```

* `license`: The package version's license. **Optional.**
    * `url`: The URL of the license file.
    * `name`: License name. [SPDX identifier](https://spdx.org/licenses/) (e.g., `Apache-2.0`, `MIT`, etc.) preferred. Omit if unknown. **Optional.**
* `createdAt`: The ISO 8601-formatted datetime string when the package version was created. **Optional.**

##### Version-specific manifests

Package collection generators should include data from the "default" manifest `Package.swift` as well as [version-specific manifest(s)](https://github.com/apple/swift-package-manager/blob/main/Documentation/Usage.md#version-specific-manifest-selection).

The keys of the `manifests` map are Swift tools (semantic) versions:
* For `Package.swift`, the tools version specified in `Package.swift` should be used.
* For version-specific manifests, the tools version specified in the filename should be used. For example, for `Package@swift-4.2.swift` it would be `4.2`. The tools version in the manifest must match that in the filename. 

##### Version-specific tags

[Version-specific tags](https://github.com/apple/swift-package-manager/blob/main/Documentation/Usage.md#version-specific-tag-selection) are not
supported by package collections.

## Example

```json
{
  "name": "Sample Package Collection",
  "overview": "This is a sample package collection listing made-up packages.",
  "keywords": ["sample package collection"],
  "formatVersion": "1.0",
  "revision": 3,
  "generatedAt": "2020-10-22T06:03:52Z",
  "packages": [
    {
      "url": "https://www.example.com/repos/RepoOne.git",
      "summary": "Package One",
      "readmeURL": "https://www.example.com/repos/RepoOne/README",
      "license": {
        "name": "Apache-2.0",
        "url": "https://www.example.com/repos/RepoOne/LICENSE"
      },
      "versions": [
        {
          "version": "0.1.0",
          "summary": "Fixed a few bugs",
          "manifests": {
            "5.1": {
              "toolsVersion": "5.1",
              "packageName": "PackageOne",
              "targets": [
                {
                  "name": "Foo",
                  "moduleName": "Foo"
                }
              ],
              "products": [
                {
                  "name": "Foo",
                  "type": {
                    "library": ["automatic"]
                  },
                  "targets": ["Foo"]
                }
              ]
            }
          },
          "defaultToolsVersion": "5.1",
          "verifiedCompatibility": [
            {
              "platform": { "name": "macOS" },
              "swiftVersion": "5.1"
            },
            {
              "platform": { "name": "iOS" },
              "swiftVersion": "5.1"
            },
            {
              "platform": { "name": "Linux" },
              "swiftVersion": "5.1"
            }
          ],
          "license": {
            "name": "Apache-2.0",
            "url": "https://www.example.com/repos/RepoOne/LICENSE"
          },
          "createdAt": "2020-10-21T09:25:36Z"
        }
      ]
    },
    {
      "url": "https://www.example.com/repos/RepoTwo.git",
      "summary": "Package Two",
      "readmeURL": "https://www.example.com/repos/RepoTwo/README",
      "versions": [
        {
          "version": "2.1.0",
          "manifests": {
            "5.2": {
              "toolsVersion": "5.2",
              "packageName": "PackageTwo",
              "targets": [
                {
                  "name": "Bar",
                  "moduleName": "Bar"
                }
              ],
              "products": [
                {
                  "name": "Bar",
                  "type": {
                    "library": ["automatic"]
                  },
                  "targets": ["Bar"]
                }
              ]
            }
          },
          "defaultToolsVersion": "5.2"
        },
        {
          "version": "1.8.3",
          "manifests": {
            "5.0": {
              "toolsVersion": "5.0",
              "packageName": "PackageTwo",
              "targets": [
                {
                  "name": "Bar",
                  "moduleName": "Bar"
                }
              ],
              "products": [
                {
                  "name": "Bar",
                  "type": {
                    "library": ["automatic"]
                  },
                  "targets": ["Bar"]
                }
              ]
            }
          },
          "defaultToolsVersion": "5.0"
        }
      ]
    }
  ]
}
```
